1. Field of the Invention
The invention relates to identifying glowing objects during a manufacturing operation and, more particularly, to a method and apparatus wherein a brightly glowing steel object may be identified.
2. Description of the Prior Art
In a steel manufacturing operation where objects such as billets are being processed, the billets typically are manufactured in one facility; cooled; and shipped to another facility where they may be worked into products. For example, billets may be made in one manufacturing facility and shipped to a rolling mill where they are reheated to temperatures on the order of 2200-2400 degrees Fahrenheit. After the billets have been reheated, they are worked to form products such as sheet steel.
Steel is manufactured in batches known as heats. Since a wide variety of alloys are manufactured, and since an individual heat will make in excess of 200 tons of a given alloy, it has become uncommon to have any two successive heats of the same alloy. Rather, it has become commonplace to make a heat to fill a given order for a specific alloy.
Since the billets of one heat often differ chemically from the next, it is obviously important to be able to avoid mixing the billets of one heat with those of another, but a problem exists in that billets can shift position in a reheat furnace. Accordingly, simply counting the billets as they enter and leave the reheat furnace does not necessarily identify billets exiting the furnace. Further it is obviously possible to simply miscount the number of billets.
Various expedients have been tried to assist in identification of reheated billets. Bricks have been placed on selected billets but they sometimes fall off or a brick may shift to another billet. Studs have been welded to, and wires wrapped around, billets. These tend to get rubbed or broken off the billets as the billets are transported through a furnace.
Since billets may be heated as high as 2400.degree. in the reheat furnace, it should be apparent that most conventional product marking techniques simply cannot be used. Whatever markings may have been tried in the past, such as the described bricks, studs and wire, are at best difficult to see because they can only be viewed from a distance and are hard to see because a hot billet glows brightly.
Because of the described and other problems inherent in billet identification, most steel manufacturing facilities have resorted to simply counting the billets and standing the consequences which result when on occasion billets get miscounted or mixed.
Another problem in steel manufacture is, it is not uncommon for slabs to have or to develop surface defects. With a heated slab there has been no successful and practical technique for determining what surface defects exist. Accordingly the normal procedure is to allow a slab to cool, inspect for and remove surface defects and then reheat the slab for further processing.